step by step solution with clear writing

A company wants to develop a group diary and a time management system for various executives. The group diary should let the executives to register the daily appointment schedule. When a meeting involving many executives is needed, the system should automatically find a common free slot in the diaries of the concerned executives and arrange a meeting at that time. The system should also inform the concern executives regarding the fixed meeting via mail. If no common slot is available, it should help the secretaries to rearrange the diaries of concern executives for making room for a common slot. Make suitable assumptions, whenever necessary. Now, perform the following for the above mentioned specification of the system. (a) Design the context level diagram and DFD at the 1 and 2 level (b) Draw use case diagram. Outline activity diagram